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STANDARDPhysics-Thermodynamics

STANDARD Physics Adiabatic Processes MCQ Question

Type: MCQ-conceptual-Medium-Class 11

When the state of a gas adiabatically changed from an equilibrium state A to another equilibrium state B, an amount of work done on the system is 35 J. If the gas is taken from state A to B via process in which the net heat absorbed by the system is 12 cal, then the net work done by the system is (1 cal = 4.19 J)

A

13.2 J

B

15.4 J

C

12.6 J

D

16.8 J

Correct Answer

Option B

Detailed Explanation

In the first-case adiabatic change, Q = 0, ΔW = −35 J. From the 1st law of thermodynamics, Q = ΔU + ΔW, or 0 = ΔU − 35 J, U = 35 J. In the second case, Q = 12 cal = 12 × 4.2 J = 50.4 J. W = ΔQ − ΔU = 50.4 − 35 = 15.4 J.

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